Re: Can you tell if your crown is bad?
Just had a similar experience with two of my rifles.
First was a 25-06 which I have had since 87 and has always shot well within an inch at 200 yds. First thing was the factory stock warped similar experience as you mention. Changed out the stock with a Fajen in about 95, which was a laminate and had aluminum pillars. The action was a good tight fit and I screwed it in and went on about my business. All fine till about a month ago when I got her out for the annual check on the sight in. First noted the scope was foggy, not an issue, I have spares. But while reoving the rings, I noted the action move slightly in the stock. Found that the wood around the action and shrunk some allowing the action to only be sitting on the tops of the pillars. A week long glass bed and back to shooting 1" groups.
Same with a .270, shot lights out every since we had it. Same load year after year, putting them into nice clover leaves at 200yds. This year couldn't keep them on a 8x11 target at 100yds. Inspected the rifle for loose screws and such, then found excessive pressure on the barrel. Pulled the action and also found that the recoil lug part of the stock had a considerable amount of powdered wood in it from the recoil lug hitting it through they years. Cleaned it out and found that the lug was then loose in the slot. So another bedding job, and back in business.
Not saying that this is your case, but could be the stock has headed in it's own direction or that the lug area could be working against you. IT is definately worth a check if you have not changed anything else.
Mike / Tx
"Heck why would I lie, most folks don't believe the truth when I tell them"